Prior art includes the following inventions;
1. Ellipsograph, U.S. Pat. No. 731,018, June 16, 1903, by R. Carlton. This instrument has a scriber arm operated by a single crank.
2. Ellipsograph, U.S. Pat. No. 1,304,494, May 30, 1919, by J. McNeil. This instrument also features synchronized cranks.
3. Ellipsograph, U.S. Pat. No. 2,913,823, Nov. 24, 1959, by P. D. Robinson. This instrument also features synchronized cranks.